Facebook UK has said that the technical difficulties experienced by many users were due to "network maintenance," but that these have now been resolved:
Earlier this morning, while performing some network maintenance, we experienced an issue that prevented some users from posting to Facebook for a brief period of time.
We resolved the issue quickly, and we are now back to 100%. We're sorry for any inconvenience we may have caused.
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The Metropolitan Police Federation, which set up the official JustGiving site, said it felt a "suitable amount" had been collected.
There is no evidence the Westminster attacker Khalid Masood was associated with so-called Islamic State or al Qaeda, the Met Police said.
Janet Ajao said in a statement: "I do not condone his actions nor support the beliefs he held that led to him committing this atrocity."